Cornerstone is a 6-star Mineral Arcanist introduced in Reverse: 1999 Version 3.8: The Temporal Scale. She specializes in Riposte damage, turning enemy attacks and allied extra actions into powerful counterattacks. Unlike traditional counterattack characters, Cornerstone can trigger her own Ripostes, giving her more control over her damage rotation.

This r1999 Cornerstone build guide covers her skills, best Psychubes, Resonance, team compositions, gameplay, Portrait upgrades, and pull advice.

Building Cornerstone and her teammates requires plenty of Insight, Resonance, and Psychube materials. If you manage multiple accounts or regularly farm resources, OSLink can help you access and manage multiple game sessions on your PC remotely. You can check auto-battle progress, collect rewards, and manage daily farming across your accounts more conveniently, making it easier to prepare the resources needed for Cornerstone and her Riposte team.

Cornerstone Overview and Role

Cornerstone is primarily a Riposte Main DPS who also provides teamwide damage mitigation. Her damage improves when allies perform extra actions and when enemies attack the team.

Her main strength is converting defensive situations into additional damage. However, Cornerstone works best with teammates who can trigger frequent Ripostes or other extra actions.

Cornerstone Arcane Skill Breakdown

The Cornerstone arcane skill kit revolves around three abilities and several interconnected resources.

Cornerstone's main mechanic is Trial and Error, which stores damage prevented by her team's defensive effect. This stored value strengthens her attacks and provides additional damage when allies perform Ripostes.

Meanwhile, Progressive Iteration increases Riposte DMG and Incantation Might. Accumulating enough stacks grants Design Revision, which further improves her powerful Delivery Feedback attack.

Her Insight III also allows her Ultimate to bypass the normal Spelldock limit, making frequent Ultimate rotations possible.

Cornerstone Best Builds and Resonance

The best builds for Cornerstone focus on improving Riposte damage, Ultimate performance, and her defensive scaling.

For Cornerstone resonance, ATK-focused builds are generally the safest choice. ATK increases her damage and raises the amount of incoming damage her defensive effects can mitigate.

Crit-focused Resonance becomes more attractive when paired with Flutterpage, whose support helps Cornerstone consistently land critical hits.

The recommended Elucidation pattern supports her Ultimate-oriented damage, especially Delivery Feedback.

Best Cornerstone Psychubes

Where Light and Shadows Rest is Cornerstone's signature Psychube and thebest overall choice for dedicated Riposte teams.

It grants Riposte DMG Bonus and increases Critical DMG whenever an ally performs a Riposte, making it especially effective alongside characters who can counterattack frequently.

Best Cornerstone Team Compositions

A strong Cornerstone team should help her generate Progressive Iteration stacks while providing additional damage, buffs, or sustain.

J with Euphoria I is one of Cornerstone's strongest partners because his repeated Ripostes help generate her resources and trigger additional damage.

Flutterpage enhances extra-action damage and provides additional AP, making Cornerstone's rotation much smoother.

Rhiannon offers valuable offensive support, although effects that prevent enemy attacks may sometimes reduce Cornerstone's opportunities to store mitigated damage.

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Cornerstone Gameplay and Rotation

Cornerstone gameplay focuses on maintaining her counterattack state and generating enough Moxie for repeated Ultimates.

A practical rotation follows this pattern:

Figure-Ground Relationship → Build Progressive Iteration → Trigger Allied Ripostes → Generate Moxie → Use Ultimate → Delivery Feedback.

Keep Inspection Process active whenever possible. Use allies such as J to trigger additional Ripostes and accelerate Cornerstone's stack generation.

After activating her Ultimate, merging and playing Cornerstone's cards can help restore Moxie for another rotation.

The goal is to maintain frequent counterattacks while timing her strongest damage around enemy attacks and accumulated resources.

Cornerstone Portrait Value

Cornerstone portrait upgrades improve her damage considerably, but her core mechanics already function at P0.

P1 is the most noticeable early upgrade, while P2 is an attractive stopping point for dedicated Cornerstone players. Higher Portrait levels are optional investments.

Pull Advice: Should You Pull Cornerstone?

Cornerstone is worth considering if you already own J (Euphoria I), Flutterpage, or other characters that support frequent extra actions and Ripostes.

She is also appealing if you need a Mineral damage dealer or enjoy counterattack-focused gameplay.

However, her damage potential depends partly on enemy behavior and team synergy. Players without suitable supports, or those who already own a strong Mineral DPS, may prefer saving their pulls.

Overall, Cornerstone is a capable but specialized Riposte carry. Prioritize her signature Psychube, choose ATK or Crit Resonance based on your teammates, and build around frequent counterattacks. Since developing a full Riposte team requires significant resources, OSLink can also help you manage multiple accounts, check AFK farming progress, and keep daily resource collection organized while preparing Cornerstone and her supports.